The present embodiments relate to a plug element and also to a plug system that may be plugged together therewith.
In order to convey extra-heavy oils or bitumen from oil sand or oil shale reserves by pipe systems that are introduced into the deposits by drilling, the flowability of the oils is to be considerably increased. This may be achieved by increasing the temperature of the reserve (e.g., reservoir), for example, by a steam assisted gravity drainage (SAGD) method.
In the case of the SAGD method, steam, to which solvent may be added, is pressed under high pressure through a pipe running horizontally within the reservoir. The heated, molten bitumen separated from the sand or rock seeps to a second pipe, placed approximately 5 m deeper, through which the liquefied bitumen is conveyed. The steam is to perform a number of tasks simultaneously (e.g., to produce the introduction of the heat energy for liquefaction, the separation from sand, and also the pressure build-up in the reservoir in order to make the reservoir geomechanically permeable for bitumen transport (permeability) and in order to enable the bitumen to be conveyed without additional pumps).
In addition to the SAGD method or instead of this method, an inductive heater may be used in order to assist or convey extra-heavy oils or bitumen.
The electromagnetically inductive heater includes a conductor loop that is placed in the reservoir and, when energized, induces eddy currents in the surrounding earth. The induced eddy currents heat the earth. In order to achieve the desired heat output densities of typically 1-10 kW per meter of inductor length, depending on the conductivity of the reservoir, amperages of several hundreds of amps are applied at frequencies of typically 20-100 kHz. For compensation of an inductive voltage drop along the conductor loop, capacitors are interposed. A series resonant circuit that is operated at the resonance frequency thereof and constitutes a purely ohmic load at the terminals is thus produced. Without these series capacitors, the inductive voltage drop of the conductor loops, which are up to a few hundred meters long, would add up from tens of kV to more than 100 kV at the connection terminals, which may hardly be managed, for example, with respect to the insulation with respect to the earth. There would have to be a compensation of the reactive power at or in the generator (e.g., oscillator).
The problem of capacitively compensated inductors with plastic-based insulation or dielectric systems lies in the upwardly limited operating temperature range. The voltage and partial discharge resistance reduces considerably when temperatures of approximately 150° C. are reached or exceeded. Whereas in the case of heavy oil reservoirs, a temperature increase of up to 50° C., for example, may be sufficient to considerably accelerate the conveyance, in the case of bitumen (e.g., oil sand) reservoirs, higher temperatures (e.g., > 100° C.) are generally necessary. In the case of hybrid methods (e.g., SAGD assisted by inductive heating, or EM-SAGD), steam from an injector or a swelling steam chamber reaches the inductor, such that temperatures above 200° C. may be present at the inductor. These temperatures may result in voltage breakdowns or partial discharges.
Capacitively compensated inductors with concentrated, ceramic-based capacitors for increased temperature resistance for inductive heating of heavy oil and oil sand deposits is an inductor having mechanically rigid concentrated capacitors, which are connected by flexible externally insulated pipes, are already known. The necessary temperature resistance is to be achieved by the use of ceramic-based capacitors. The same demand, however, on the electrical insulation properties is also placed on the external insulation of the pipes. Since, however, the external insulation does not simultaneously have the function of a dielectric, the layer thickness may be increased. However, the demand with regard to temperature resistance and flexibility remains.
In addition, distributed capacitors based on coaxial line structures are known. Resonance lengths around 10 m or greater and capacitor portions with 1-2 m length are formed. To this end, a separate external insulation is to be provided.
DE 20 2007 005 696 U1 discloses a tubular structural component for producing line, shafts, pipe fittings and the like for receiving aggressive liquids or vapors, including a pipe shaft and end-face pipe ends. The ends are designed in a manner complementary to adjacent pipes in order to produce a tight connection thereto. The pipe shaft consists of a cement-bonded concrete, and the pipe ends consist of a concrete that is resistant to chemicals. The pipe shaft, on the inner periphery thereof, has a layer that is resistant to chemicals. The concrete, which is resistant to chemicals, of the pipe ends adjoins the layer resistant to chemicals in each case in a closed peripheral contact joint. Units for increasing the flow resistance are arranged in the contact joint, are connected tightly to the layer resistant to chemicals, and are connected tightly to the concrete resistant to chemicals.
A double-chamber pipe system for rainwater collection systems is known from DE 94 00 877 U1. The double-chamber pipe system includes various double-chamber elements, such as a transition piece/connection piece, straight pipe, vertical curve, horizontal curve and branch piece. The shaping, dimensions, and material nature of the double-chamber elements resemble conventional pipe elements with sleeves and ring seals but in the inner region, have a partition wall halving the inner diameter. The inflow of rainwater to the container is controlled in the upper chamber, and the return flow/overflow of the rainwater from the container into the conventional sewer system is controlled in the lower chamber.